JP3050637B2 - Multiplex transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a so-called CSMA / CD (Carr
The present invention relates to a multiplex transmission method using an ier Sense Multiple Access / Collision Detection) transmission method.

[0002]

2. Description of the Related Art Conventionally, in a multiplex transmission system of this type, each multiplex node is commonly connected to a multiplex transmission line (data bus) composed of a pair of electric wires. Each multiplex node is provided with a communication control circuit composed of a communication IC and a central processing unit (hereinafter, referred to as a “CPU”), and transmits data for each frame to a data bus by a CSMA / CD method. Simultaneously transmitting the data to the other multiplex nodes, and providing an acknowledgment signal (ACK signal) area at the end of the frame, and allowing each multiplex node that has normally received the frame to assign a predetermined bit position to the ACK signal area. ACK signal.

The communication control circuit of the multiplex node controls the communication of the above-mentioned frame, and detects an error in the received data when receiving the frame. Also, at the time of frame transmission, monitoring of collisions on the data bus of data transmitted by the multiplex node of the own station and the multiplex node of the other station on the data bus and carrier sense for detecting an empty state of the data bus are performed.

[0004]

However, in the above system, the communication IC of each multiplex node is provided with a circuit for monitoring the data bus, so that the configuration becomes complicated and the communication IC is controlled. CPU must be provided. For this reason, there is a problem that the manufacturing cost of the multiple nodes increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and reduces the number of communication IC gates of some of the multiplex nodes connected to a data bus and reduces the number of CPUs.
It is an object of the present invention to provide a multiplex transmission system capable of simplifying the configuration by reducing the cost, reducing the production cost, and reducing the traffic amount of the data bus.

[0006]

According to the present invention, there is provided, in accordance with the present invention, at least two multiplex nodes interconnected via a common multiplex transmission line, wherein one of the multiplex nodes is a frame. In a multiplex transmission method of transmitting data every time and returning a reception confirmation signal to the multiplex transmission line when another multiplex node receives a frame normally, one of the multiplex nodes monitors the use state of the multiplex transmission line. When a transmission request is generated, the multiplex transmission path waits until it becomes unused, and returns a reception acknowledgment signal area corresponding to the reception acknowledgment signal of the reception multiplex node. A data request frame provided with a return data area allocated corresponding to the data is transmitted, and the reception multiplex node that has normally received the data request frame is transmitted to the reception multiplex node. The response data area and the acknowledgment signal area to respond, multiplex transmission method that returns a specific reception acknowledgment signal and a predetermined data to the receiving multiplex node is provided.

[0007]

When the receiving multiplex node receives the frame transmitted from the transmitting multiplex node, the receiving multiplex node transmits predetermined data of the own node to the transmitting multiplex node together with a reception confirmation signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram showing one embodiment of a system used for the multiplex transmission system according to the present invention.
A multiplex transmission system using such a CSMA system includes, for example, a multiplex transmission system for automobiles.

In the figure, each multiplex node 10-40
Connected via a data bus 50,
Reference numerals 0, 20, and 30 each include a communication control circuit of a communication IC for performing frame communication control and a CPU for monitoring the data bus 50 as in the conventional example, and multiplex-transmit data frames. In the embodiment, for convenience of explanation, the communication control circuit 10a of the multiplex node 10 and the CPU 10
Only b is shown. As shown in FIG. 2, the reception multiplex node 40 is constituted by a communication control circuit 40a of a communication IC. 40b and a lamp group 40c are connected, and the lamp group 40c is connected in accordance with data 3 and 4 of the data frame received from the multiplex node 10.
c is turned on, and the on / off data of the switch group 40b is set to data 1 and 2 as shown in FIG.
It is output to the data bus 50 together with the CK signal. That is, each pin of the inputs 1 and 2 corresponds to each bit of the data 1 and 2, and each pin of the outputs 1 and 2 corresponds to each bit of the data 3 and 4.

As shown in FIG. 3A, the data frame F used in this embodiment has a frame structure having SOM, PRI, ID data, data, CRC, ACK signal areas, and the like. Here, SOM is a specific bit indicating the start of the frame, PRI (priority) is data indicating the priority of the frame, ID data is an address indicating the destination, an address indicating the own station, and the frame length. The CRC is data for error detection, and the ACK signal area is composed of a bit area corresponding to the address of each multiplex node.
Is a specific bit indicating the end of a frame. Also,
The frame has a return data area divided for each predetermined data length and assigned corresponding to data returned from the receiving multiplex node.

In the multiplex transmission system for automobiles, the multiplex nodes 10, 20, 30 include, for example, a front multiplex node, a meter multiplex node, a rear multiplex node, etc., and multiplex transmission of vehicle driving information for each data frame. ing.
The multiplex node 40 may be a combination switch multiplex node or the like, and each receiving multiplex node transmits return data in synchronization with a return data area of a data frame transmitted from the transmission multiplex node 10.

Next, the operation of multiplex transmission in the system of the present invention will be described. In the embodiment, a case will be described in which the multiplex node 10 is a transmission multiplex node and the multiplex node 40 is a reception multiplex node, and the ID of the multiplex node 40 is determined to be, for example, “$ 80”. First, the CPU 10b of the multiplex node 10 waits for the data bus 50 to become unused. When the data bus 50 enters an unused state, the communication control circuit 10a
Is given a data transmission instruction. The communication control circuit 10a
When the transmission instruction is given, the data frame F shown in FIG. 3A is transmitted to the receiving multiplex node 40 via the data bus 50 by the CSMA / CD system.

When receiving the data frame F, the multiplex node 40 checks the ID data in the frame, and
If the D data is the same as the preset ID ($ 80) of the own node, it is determined that the request is a transmission request, and then the data 1,
Send 2. Then, the CRC is calculated based on the PRI, ID, data 3 and 4 and the data 1 and 2 to be transmitted, and the ACK signal is transmitted to the multiplexing node 10 when the CRC is the same as the CRC of the data frame F when they are the same. Also,
If the CRCs are not the same, the ACK signal is not returned.

The CPU 10b of the multiplex node 10 transmits PRI, ID, data 3, 4 and received data 1,
2 and calculate the CRC of the data frame F.
Transmit as C. If the CPU 10b does not receive the ACK signal from the multiplex node 40, the CPU 10b regards the captured data 1 and 2 as errors and discards the data. That is, as shown in FIG. 2, when the data 3 and 4 from the multiplex node 10 are set to “$ FF00”, the multiplex node 40
When the above data 3 and 4 are received, the lamp of output 1 is fully lit and the lamp of output 2 is completely extinguished in accordance with each bit of data 3 and 4, The corresponding data 1 and 2, that is, “$ F0F0”, are transmitted to the multiplex node 10 via the data bus 50.

The multiple nodes 20 and 30 are
Receives the data frame transmitted from the multiplexing node 10 as in the prior art, and returns an ACK signal to the multiplex node 10 if there is no error. Therefore, in the present embodiment, the transmission multiplex node cyclically transmits a data frame having a return data area assigned corresponding to the data length of data returned from the reception multiplex node,
When the data frame is received, the data allocated to the return data area is transmitted in synchronization with the return data area. Therefore, the reception multiplex node 40 does not require a collision control circuit, a carrier sense circuit, and the like. The number of gates can be reduced. Further, since the receiving multiplex node 40 only needs to input and output data, a CPU is not required, and the manufacturing cost of the system can be reduced.

In the first embodiment, since it is not known when the switch of the receiving multiplex node changes, the multiplex node 10 frequently sends out the data frame of the transmission request to the data bus, and switches the switching state of the receiving multiplex node. Needs to be confirmed, and the traffic volume of the bus may be large. Therefore, in the present invention, in addition to the above-described first embodiment, for example, the reception multiplex node includes the inputs 1 and 2 shown in FIG.
When at least one switch state changes (the switch state changes from on to off or from off to on), the event generation signal ES shown in FIG. 3C is transmitted first, and the multiplex node 10 When the above ES is received, FIG.
It is also possible to transmit the data frame shown in (a), make a data transmission request, and receive the data 1 and 2 shown in FIG. 3 (c) from the receiving multiplex node 40. It is. Thus, the signals on the data bus are as shown in FIG.

Therefore, in the second embodiment, unlike the case of the first embodiment, it is not necessary to check the switch state of the receiving multiplex node when the ES is not used, and the traffic volume of the bus can be reduced. it can. The above E
If S is set to the signal with the highest priority, the ES of the receiving multiplex node always remains preferentially even when it collides with a transmission frame from another multiplex node. / A collision control circuit for controlling transmission suspension is not required, thereby reducing the number of gates of the communication IC. However, in this case, since the receiving multiplex node actively performs transmission, carrier sense is necessary.

In FIG. 1, if the multiplex node 10 is set as a transmission multiplex node and the multiplex nodes 20, 30, and 40 are set as reception multiplex nodes, the presence of a plurality of reception multiplex nodes will prevent the ES from occurring. Since it cannot be distinguished from which node the data frame was transmitted, the data frame of the transmission request must be transmitted to all the receiving multiplex nodes, and the traffic volume of the data bus increases.

Therefore, in this embodiment, as shown in FIG. 4, the length of the ES of the receiving multiplex node 20 is 8 bits, the length of the ES of the receiving multiplex node 30 is 7 bits, and the length of the ES of the receiving multiplex node 40 is The length of the ES is set to 6 bits.
Thus, when the input data changes, the reception multiplex nodes 20, 30, and 40 transmit an event occurrence signal (ES) having a different bit length corresponding to each reception multiplex node to the data bus 50, and the transmission multiplex node 10 , ES above
, The corresponding reception multiplex node is recognized from the bit length of the ES, and a data frame F described later is transmitted to the reception multiplex node that transmitted the ES.

Further, E is simultaneously received from three reception multiplex nodes.
When S is transmitted, the signal on the data bus has an 8-bit length and becomes the same as the ES of the reception multiplex node 20. Therefore, when an 8-bit length ES is received, all the signals are received. A data frame F is transmitted to the reception multiplex nodes 20, 30, and 40, and a transmission request is made.
If S is received, a data frame F is transmitted to the reception multiplex nodes 30 and 40 to make a transmission request. If a 6-bit ES is received, the reception multiplex node 40 A data frame F is transmitted to request transmission. Each receiving multiplex node receiving the transmission request,
The predetermined data in the own node is transmitted to the transmission node 10.

Therefore, in the present embodiment, the transmission multiplex node that has received the ES sends, to the reception multiplex node, a data frame having a return data area allocated according to the data length of the data returned from the reception multiplex node. Send,
When the receiving multiplex node receives the data frame,
Since the data allocated to the return data area is transmitted in synchronization with the return data area, the reception multiplex node does not require a collision control circuit or a carrier sense circuit, etc.
The number of gates of the communication IC can be reduced. Also,
Since the receiving multiplex node 40 only needs to input and output data, a CPU is not required, and the manufacturing cost of the system can be reduced. Further, in this embodiment, since the length of the ES is changed for each reception multiplex node, the transmission multiplex node only has to make a transmission request to a specific reception multiplex node, and the traffic volume of the bus is reduced. can do.

As another embodiment of the present invention, similarly to the above, the length of the ES of the receiving multiplex node 20 shown in FIG.
The 7-bit length, the length of the ES of the reception multiplex node 40 is set to 6 bits, and each reception multiplex node is provided with monitoring means for monitoring a transmission request to its own node, for example, a counter circuit. If there is no transmission request to the own node within a predetermined time, the ES is retransmitted.

In this embodiment, when the transmission multiplex node receives an 8-bit length ES, the reception multiplex node 20
, Only when a 7-bit ES is received, a transmission request is made only to the receiving multiplex node 30, and when a 6-bit ES is received, the receiving multiplex node 40 is received. It is only necessary to make a transmission request to. When the ESs are transmitted from the receiving multiplex nodes 20 and 30 at the same time, the transmitting multiplex node first makes a transmission request only to the receiving multiplex node 20. Since the receiving multiplex node 30 does not have a transmission request to its own node even after a predetermined time has passed,
The transmission multiplex node makes a transmission request to the reception multiplex node 30 by retransmitting the ES.

Therefore, in the above other embodiment, the number of transmission requests can be further reduced, and the traffic volume of the bus can be further reduced. However, in the above other embodiment, if the transmission multiplex node fails, the retransmission of the ES by the reception multiplex node is repeated indefinitely, so that the retransmission of the ES may be stopped at a certain number of times. desirable.

When the priority of data transmission is set in the receiving multiplex nodes, the ES of the plurality of receiving multiplex nodes can be set by increasing the length of the ES as the node has a higher priority. Even in the case of collision, there is an advantage that transmission delay of a node having a higher priority can be reduced.

[0026]

As described above, according to the present invention, at least two multiplex nodes are connected to each other via a common multiplex transmission line, and one of the multiplex nodes transmits data for each frame. In a multiplex transmission method in which a reception confirmation signal is returned to the multiplex transmission line when another multiplex node receives a frame normally, any one of the multiplex nodes has monitoring means for monitoring a use state of the multiplex transmission line, When a transmission request is generated, the multiplex transmission path is waited until it becomes unused, and the acknowledgment signal area allocated in response to the acknowledgment signal of the receiving multiplex node and the acknowledgment signal area allocated in response to the return data are allocated. A data request frame provided with a return data area, and the reception multiplex node that has normally received the data request frame transmits a reception acknowledgment signal area corresponding to the reception multiplex node. And the return data area, the reception acknowledgment signal specific to the reception multiplex node and the predetermined data are returned, so that the CPU of some of the multiplex nodes connected to the data bus is omitted and communication is performed. IC
Therefore, the collision control circuit and the carrier sense circuit can be omitted, the manufacturing cost can be reduced, and the traffic amount of the data bus can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a system in a multiplex transmission system according to the present invention.

FIG. 2 is a diagram illustrating a configuration of a communication control circuit illustrated in FIG. 1;

FIG. 3 is a diagram showing an embodiment of a data frame and return data to be transmitted.

FIG. 4 is a diagram illustrating the length of an event occurrence signal of each reception multiplex node illustrated in FIG. 1;

[Description of Signs] 10 to 40 Multiple nodes 10a, 40a Communication control circuit 10b Central processing unit (CPU) 50 Data bus F Data frame

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kyosuke Hashimoto 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Teruhisa Inoue 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Inside Electric Industry Co., Ltd. (72) Inventor Seiji Hirano 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (72) Osamu Dohei 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Stock In-company (72) Inventor Hiroaki Sakamoto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-64-27338 (JP, A) JP-A-60-79843 (JP, A) JP-A-2-161846 (JP, A) JP-A-59-205846 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/40

Claims (6)

(57) [Claims] 1. At least two multiplex nodes mutually connected via a common multiplex transmission line, one of which transmits data for each frame, and the other multiplex node normally receives a frame. In the multiplex transmission method of returning a reception acknowledgment signal to the multiplex transmission path when the multiplex transmission path is used, any one of the multiplex nodes has a monitoring unit for monitoring a use state of the multiplex transmission path. Waiting for the multiplex transmission path to become unused, a data request including a reception acknowledgment signal area allocated corresponding to the reception acknowledgment signal of the reception multiplex node and a return data area allocated corresponding to the return data. The receiving multiplex node, which has transmitted the frame and received the data request frame normally, stores the received multiplexing node in a reception acknowledgment signal area and a return data area corresponding to the receiving multiplex node. A multiplex transmission method characterized by returning an acknowledgment signal unique to the network and predetermined data. 2. The reception multiplex node transmits an event occurrence signal when input data changes, and transmits the data request frame from the multiplex node that has received the event occurrence signal. Multiplex transmission system. 3. The multiplex transmission system according to claim 2, wherein said event occurrence signal is a signal having the highest priority. 4. The multiplex transmission system according to claim 1, wherein when a plurality of said reception multiplex nodes exist, the length of said event occurrence signal differs for each node. 5. The multiplex transmission according to claim 4, wherein the event occurrence signal is a signal indicating a priority of frame transmission, and the event occurrence signal corresponding to a receiving multiplex node having a higher priority has a longer signal. method. 6. The receiving multiplex node, after transmitting an event occurrence signal, monitors a data request to the own node,
6. The multiplex transmission system according to claim 1, wherein the event occurrence signal is retransmitted when there is no data request within a predetermined time.